Method and medical x-ray system for monitoring surgical interventions with x-ray imaging

Abstract

In order to reliably monitor surgical interventions with elongated implants with as low X-ray doses as possible, a method for monitoring surgical interventions with X-ray imaging is provided, which is carried out with an imaging system which can be adjusted to different angles and which comprises an X-ray source and an X-ray detector, an implant with a tip is moved forward along a movement axis in an anatomy of an examination subject with the tip.

Description

Technical Field

[0001] The invention relates to a method for monitoring surgical interventions using X-ray imaging and to a medical X-ray system for carrying out a method of this type. Background Art

[0002] In orthopedic and trauma surgery, screws, wires and other implants need to be placed into bones. This is a major challenge, as the respective implant must be positioned very precisely in narrow channels depending on the patient anatomy and the intervention to be performed, in order to avoid damage to the surrounding tissue and ensure that the intervention proceeds smoothly. High-quality imaging for monitoring the intervention during implant introduction is therefore essential.

[0003] There are two different possibilities for this, each of which can be chosen depending on the complexity of the intervention. In simpler cases, a large number of 2D projection images are recorded at at least two different angles, wherein the angles are usually switched between in order to obtain a three-dimensional understanding of the implantation process relative to the patient's anatomy. In particularly complex cases, surgical navigation systems are used in combination with 3D CBCT (cone beam CT) imaging and external tracking in order to monitor the introduction of the screw. In this case, an external camera system measures the relative position between the patient's anatomy and the implant with the aid of markers that are fixed to both. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method which simplifies the monitoring of an implant, for example its introduction into a bone, in particular in the case of less complex surgical interventions; furthermore, the technical problem to be solved by the present invention is to provide a medical X-ray system suitable for implementing the method.

[0005] According to the invention, this object is achieved by a method for monitoring surgical interventions using X-ray imaging according to claim 1 and a medical X-ray system according to claim 11. Preferred embodiments of the invention are respectively the technical solutions of the dependent claims.

[0006] According to the present invention, a method for monitoring surgical intervention using X-ray imaging is provided, wherein the X-ray imaging is performed using a shooting system that can be adjusted to different angles, the shooting system comprising an X-ray light source and an X-ray detector, wherein an implant having a tip moves forward along a motion axis in (or on) the anatomical structure of an inspection object using the tip, the method comprising the following steps: shooting a first projection image of the implant at a first angle, and after the implant moves forward, shooting a third projection image of the implant at a third angle, optionally determining an initial position of the tip of the implant on the first projection image, determining an advanced position of the tip of the implant on the third projection image, determining a first epipolar line for the advanced position of the tip in the first projection image with the aid of an epipolar geometry relationship determined by the first angle and the third angle, and simultaneously showing the first projection image and the third projection image, wherein the determined epipolar line is shown in the first projection image.

[0007] The method allows the user to visualize the updated advanced position of the tip of the implant particularly quickly and easily in at least one additional projection image at a further angle, and if necessary even in a plurality of projection images at a plurality of angles, without additional adjustment of the recording system. The user does not have to record an updated projection image for each angle, but can use the epipolar line to update and display the advanced position of the tip: the updated advanced position can be visualized in the initial first projection image recorded before the movement with the help of the updated third projection image. The method not only saves X-ray dose, but also avoids a lot of time and effort in adjusting the recording system. At the same time, good and precise monitoring of the intervention and the implant moving forward is also achieved. Overall, the radiation exposure to the patient and thus the risk to the patient's health is reduced, and the treatment results are maximized. The method allows the user to have a more intuitive understanding of the three-dimensional intervention scene. In addition, the simultaneous display of at least two or even more projection directions helps the user (such as a surgeon) to assess the situation more reliably. In particular, previously unused geometric information can be used. The method enables quasi-three-dimensional observation without the need for actual 3D imaging.

[0008] The "tip of the implant" is to be understood below as the point of the implant which is arranged furthest forward in the direction of movement in the direction of advancement, wherein this does not necessarily mean a sharply focused implant. It is firstly important that a "point" is used for determining the epipolar line, that is to say not a shape which expands significantly in different directions.

[0009] The term “angle” is to be understood as meaning the projection geometry of the recording system, ie the position of the x-ray source and the x-ray detector as well as the projection angle of the x-ray radiation (central beam) relative to the examination object.

[0010] It should be noted that the first angle is different from the third angle, because otherwise it would not be possible to achieve epipolar geometry.

[0011] According to the design of the present invention, an additional step is performed: before the forward movement, a second projection image of the implant is taken at a second angle different from the first angle, the initial position of the tip of the implant is determined on the second projection image, a second epipolar line is determined in the second projection image for the advanced position of the tip by means of the epipolar geometry determined by the second angle and the third angle, and the second projection image is simultaneously shown with the first projection image and the third projection image, wherein the determined second epipolar line is shown in the second projection image. In summary, three angles are used here so that the user can obtain a better observation of the intervention. Through different angles, especially as different as possible, the user obtains a quasi-three-dimensional impression of the intervention. Positions that are difficult to pass through for the forward movement of the implant can be observed and evaluated from different directions. To this end, only two projection images need to be taken at different angles before the implant moves.

[0012] According to another design of the present invention, the (projected) axis of motion of the forward motion of the tip of the implant is also shown (e.g., gradually displayed) in the first projection image and / or the second projection image. In this way, the user can clearly recognize how the forward motion of the implant may act in the projection plane. In particular, the axis of motion is determined by the extrapolation method of the longitudinal axis of the implant according to the first projection image and / or the second projection image, and is displayed in the first projection image and / or the second projection image. Then the implant can be identified, for example, by segmentation and / or image recognition, and the longitudinal axis of the implant is determined thereby. This can be implemented simply and quickly in particular.

[0013] According to another embodiment of the invention, the corresponding intersection of the epipolar line with the axis of motion (e.g., the longitudinal axis obtained by extrapolation) is determined and displayed. In this way, the current advanced position of the tip can be displayed in a simple and well-recognizable manner in the first and second projection images. In this way, the current advanced position can be quickly and accurately displayed on more (or any number of) projection images, wherein only a single current projection image is actually required.

[0014] According to the design of the invention, segmentation and / or image recognition are respectively performed to determine the initial position and / or the advanced position and / or the implant on the projection image. For this purpose, known software algorithms can be used.

[0015] The three-dimensional impression of the advancement movement of the implant is enhanced if the third angle is different from the first angle and the second angle.

[0016] According to the design of the present invention, the first projection image, the second projection image and the third projection image are shown side by side and / or one above the other. These projection images can be arranged according to user needs in order to obtain the best observation of the intervention. Multiple display units (such as displays, touch screens, etc.) can also be used.

[0017] According to another embodiment of the present invention, the movement axis is gradually displayed and / or drawn and / or marked in the projection image or visually displayed in another way. It can also be implemented in color as required.

[0018] According to another design of the present invention, at least one additional projection image is captured at a third angle, another advanced position of the tip of the implant is determined in each of the additional projection images, and another epipolar line is determined in the first projection image and the second projection image by the epipolar geometric relationship determined by the first angle and the third angle and / or the second angle and the third angle together with the advanced position of the tip, and the determined other epipolar line is shown in the first projection image and the second projection image. In this way, any number of advanced positions of the tip of the implant can be visualized and the entire intervention can be optimally monitored.

[0019] In addition, the present invention also includes a medical X-ray system for implementing the above method, which has an X-ray imaging device, the X-ray imaging device is used to take X-ray images and has a shooting system that can be adjusted to different angles, the shooting system has an X-ray light source and an X-ray detector; the medical X-ray system has a system control unit, which is used to control the medical X-ray system; the medical X-ray system has an image system, which is used to analyze X-ray images, in particular for image recognition; the medical X-ray system has an evaluation unit, which is used to determine the epipolar line; the medical X-ray system has a display unit, which is used to display the X-ray image and the epipolar line. In an advantageous manner, the X-ray system has at least one motion and / or angle sensor and / or encoder for measuring the adjustment of the motion or rotation axis. In particular, multiple or all motion and rotation axes of the X-ray system are equipped with motion and angle sensors and / or encoders so that external features of the projection geometry can be derived therefrom. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention and further advantageous embodiments according to the features of the dependent claims are explained in detail below with reference to the exemplary embodiments schematically shown in the drawings, but the invention is not limited to these exemplary embodiments. In the drawings:

[0021] Figure 1 A flow chart showing the steps of a method for monitoring a surgical intervention using X-ray imaging;

[0022] Figure 2 Another flow chart showing the steps of a method for monitoring a surgical intervention using X-ray imaging;

[0023] Figure 3 A diagram showing the epipolar geometry when three projection images are captured according to the method;

[0024] Figure 4 shows a view showing three projection images with epipolar lines according to the method;

[0025] Figure 5 A view showing a medical X-ray system for implementing the method; and

[0026] Figure 6 The known diagram shows the epipolar geometry when an image of an object is captured from two projection directions. DETAILED DESCRIPTION

[0027] exist Figure 1 and Figure 2 , the steps of two embodiments of a method for monitoring a surgical intervention with the aid of X-ray imaging are shown, which is performed by means of a recording system that can be adjusted to different angles.

[0028] The method is used, for example, to monitor interventions on patients in orthopedic interventions, wherein, for example, screws, wires or other implants are introduced into tissue and / or bone. The monitoring method makes it possible to obtain a comprehensive monitoring of the progress of the implant movement with low X-ray burden. After the initial recording from at least two different angles, the user only needs to record the projection image from one projection direction and can see the advancement of the implant from two or more projection directions. This allows the implant to be positioned very accurately and avoid damage to the patient's surrounding tissue in the intervention area.

[0029] Monitoring is performed by X-ray imaging performed by a recording system of an X-ray system that can be adjusted to different angles (projection direction), for example in the form of a C-arm, wherein the C-arm has an X-ray source and an X-ray detector. During the intervention, an implant having a front point or a tip moves forward linearly along the axis of motion in the anatomical structure of the object of examination with the tip. The vast majority of implants extend longitudinally and therefore have a clear longitudinal axis, for example the implant is a screw, a microcatheter, a guide wire or a nail. For simplification, in most cases, for example in orthopedic interventions, it can be assumed that the longitudinal axis corresponds to the axis of motion / feed axis. This can be applicable to the current situation. As an alternative, the axis of motion can also be determined, calculated or estimated in other ways.

[0030] exist Figure 6 The known geometric relationship and working method when determining the epipolar line according to the general epipolar geometric relationship are shown in FIG: From the point object O and its environment from two different projection directions from the x-th projection center S x Take the xth image I x And from the y-th projection center Sy Take the yth image I y (For example, using a camera). Object O in image I x and I y The above is shown as the x-th object projection O x and the y-th object projection O y . xy epipolar plane E xy Through the x-th projection center S x and the y-th projection center S y and the real 3D position of the object O. The xy epipolar plane E xy With the xth image I x The intersection of the two forms the xth epipolar line E x , and with the y-th image I y The intersection of the two forms the yth epipolar line E y Such geometric relationships are basically known in the prior art, see for example https: / / de.wikipedia.org / wiki / Epipolargeometrie.

[0031] The invention utilizes the fact that in X-ray imaging at any angle of a recording system (e.g. a C-arm), the spatial projection geometry is known or can be determined, for example, by means of sensors / encoders on the axis. It is also utilized that when a point, such as the tip of an implant, moves linearly forward, its axis of motion can be determined or estimated and displayed in the projection image.

[0032] In the first step 10 ( Figure 1 ), a first projection image I1 of an implant arranged in an examination object (eg, a patient's body) is captured at a first angle—for example, see Figure 3 A three-dimensional spatial relationship is described in which the first projection center S1 corresponds, for example, to the position of the focus of the X-ray source 31 at a first angle, and the projection image I1 corresponds to the position of the X-ray detector at the first angle. The shooting of the first projection image can be carried out, for example, before the forward movement of the implant to be monitored begins. Then, for example, in an intervention in which an implant (such as a screw) is to be implanted into a bone, the implant can be positioned in advance on the cortex (cortical bone) as a starting position for passing through the bone, and the axis of movement can be fixed (not part of the method). The shooting system (C-arm) can be oriented according to the desired axis of movement of the implant for shooting the first projection image.

[0033] In particular, the implant 20 and the tip 21 of the implant are imaged in the first projection image I1 , wherein the position of the tip 21 is also referred to here as the initial position.

[0034] After the forward movement of the implant and its tip is completed, a third projection image I3 of the implant is recorded in a second step 11 at a third angle of the recording system, which is different from the first angle. The implant 20 and the tip 21 of the implant are also imaged in the third projection image I3, wherein the tip 21 has an advanced position (i.e. after the forward movement is completed). Figure 3 The three-dimensional spatial relationship, the third projection center S3 used for this purpose, and the projection image I3 are shown in FIG. 1 , wherein the third projection center is equivalent to the position of the focus of the X-ray light source 31 at the third angle, and the projection image is equivalent to the position of the X-ray detector at the third angle.

[0035] In the optional third step 12, the initial position of the tip of the implant is determined on the first projection image I1, for example, by segmentation software or image recognition software running in the image system. This type of image recognition method has been known for a long time. In addition, the implant (within the imaged area) can also be fully identified so that, for example, its longitudinal axis can be determined or estimated. The third step 12 can also be implemented at other times, for example directly after shooting. In the fourth step 13, the forward position of the tip of the implant (optionally also the implant) is determined on the third projection image I3. This can also be implemented by segmentation or image recognition software known on the image system.

[0036] In the fifth step 14, the known projective geometric relationship between the first angle and the third angle is used, such as Figure 3 As shown - a first epipolar line E1 is determined in the first projection image I1, which represents the projection of the advanced position of the tip determined by the third projection image on the first projection image I1. The first epipolar line E1 is formed by projecting a spatially arranged connecting line H3 between the third projection center S3 and the advanced position of the tip of the implant onto the first projection image I1.

[0037] In a sixth step 15, the first projection image I1 and the third projection image I3 are displayed, for example, on a display unit or monitor (for example as a split screen), wherein the first epipolar line E1 is imaged, for example faded in, superimposed, drawn in, etc. in the first projection image I1. The projection images can be displayed, for example, next to each other and / or one above the other. The display is thus performed so that the user can observe the intervention particularly clearly. Figure 4 An example of such a display is shown in FIG. 5 , wherein a second projection image I2 (which will be described in detail below) is also shown next to the first projection image I1 and the third projection image I3 .

[0038] In a seventh step 16, the predicted movement axis A1 of the tip of the implant is shown, for example faded in, superimposed or drawn in, on the first projection image I1—for example, Figure 3 and Figure 4To this end, the movement axis A1 is determined in advance, for example calculated or estimated. The movement axis A1 of the tip of the implant in the first projection image I1 can be determined, for example, as an extension or extrapolation of the longitudinal axis of the implant 20 (or its projection on the first projection image I1). In an eighth step 17, the advanced position P of the tip of the implant in the first projection image I1 is formed by the intersection of the movement axis A1 and the first epipolar line E1 in the first projection image I1. F1 .

[0039] exist Figure 2 , wherein in the ninth step 100 (instead of the first step 10), a first projection image I1 is captured at a first angle before the forward movement of the implant, and a second projection image I2 is captured at a second angle, wherein the two angles are different. In particular, significantly different angles can be used in order to obtain a view that is as comprehensive as possible. In another embodiment (not shown), a plurality of projection images can also be captured at a plurality of different angles, depending on how many viewing angles the user wishes. Figure 2 The second step 11 in Figure 1 The method in corresponds to .

[0040] Optionally, in a tenth step 120 (instead of the third step 12 ), the initial position of the tip of the implant is determined in the first and second projection images I1 and I2 (alternatively also in other projection images), again for example by segmentation or image recognition software. Figure 2 The fourth step 13 in Figure 1 The method in corresponds to .

[0041] Subsequently, in the eleventh step 140 (instead of the fifth step 14), the first epipolar line E1 on the first projection image I1 is determined using the known projection geometric relationship between the first angle and the third angle, the first epipolar line E1 representing the projection of the advanced position of the tip determined by the third projection image on the first projection image I1; and in addition, the second epipolar line E2 on the second projection image I2 is determined using the known projection geometric relationship between the second angle and the third angle, the second epipolar line E2 representing the projection of the advanced position of the tip determined by the third projection image on the second projection image I2. The first epipolar line E1 is formed by projecting the spatial line H3 between the third projection center S3 and the advanced position of the tip of the implant onto the first projection image I1, and the second epipolar line E2 is formed by projecting the spatial line H3 between the third projection center S3 and the advanced position of the tip of the implant onto the second projection image I2.

[0042] As an alternative, further epipolar lines can also be determined on further projection images.

[0043] Subsequently, in a twelfth step 150 (instead of the sixth step 15), the first projection image I1, the second projection image I2 and the third projection image I3 are shown, for example, on a display unit or a monitor, wherein the first pair of epipolar lines E1 are shown, for example faded in, superimposed, drawn in, etc. in the first projection image I1 and the second pair of epipolar lines E2 are shown, for example faded in, superimposed, drawn in, etc. in the second projection image I2—see Figure 3 The projected images can be shown, for example, side by side with one another and / or one above the other - see Figure 4 If desired, multiple projected images can also be shown.

[0044] In the thirteenth step 160 (instead of the seventh step 16), the movement axis A1 of the tip of the implant in the first projection image I1 and the movement axis A2 of the tip of the implant in the second projection image I2 are shown, for example faded in, superimposed or drawn in, - see Figure 3 and Figure 4 For this purpose, the movement axes A1 and A2 are determined in advance, for example calculated or estimated. The movement axes can be determined, for example, as an extension or extrapolation of the longitudinal axis of the implant 20 (or as a corresponding projection).

[0045] In a fourteenth step 170, the advanced position P of the tip of the implant on the first projection image I1 is formed by the intersection of the movement axis A1 and the first epipolar line E1 on the first projection image E1. F1 , and the intersection of the movement axis A2 and the second epipolar line E2 on the second projection image E2 forms the advanced position P of the tip of the implant on the second projection image I2 F2 --See Figure 4 .

[0046] The order of the steps can generally also be changed.

[0047] In order to visualize the further forward movement of the implant during the intervention, the method can be repeated as often as desired, or the updated projection images are respectively taken with the further updated forward position of the tip, and the epipolar line is determined and shown accordingly. The entire intervention or the entire forward movement can be gradually visualized in this way. The current projection image can be shown on the display together with the projection image taken before the forward movement, and the current forward position with the current epipolar line is shown on the latter. The axis of motion can be maintained, thereby forming a further updated forward position through the intersection.

[0048] The superposition of the polar line and the axis of motion provides the user with valuable additional information that approximates a three-dimensional representation. The advancement of the implant, for example in bone or tissue, can thus be continuously observed. Since the direction of the axis of motion remains constant, the updated advanced position of the tip can be visualized on multiple projection images and an intuitive understanding of the three-dimensional intervention scenario is achieved.

[0049] The method saves time and patient dose, because old projection images from other angles do not have to be updated, but the current advanced position of the tip of the implant can still be always shown. In addition, the simultaneous visualization of multiple projection directions helps the user to accurately and reliably estimate the situation. In particular, the proposed superposition uses previously unused geometric information. The main difference between the method and the navigation-based solution is that it does not rely on 3D imaging and external tracking systems. The method is simple, low-cost, has low hardware requirements, and saves time and X-ray dose.

[0050] exist Figure 5 , a medical X-ray system 38 for implementing the method is shown. It has, for example, a shooting system in the form of a C-arm 30, including an X-ray source 31 and an X-ray detector 32, and the C-arm 30 can be adjusted to multiple angles. The medical X-ray system 38 is controlled by a system controller 33, for example, for implementing the method and for shooting projection images. In addition, the medical X-ray system 38 also has an image system 35, which is configured to process the projection images, in particular, by software for segmentation and / or image recognition. The image system 33 or corresponding software can identify, for example, objects, such as implants and their tips in the projection images. In addition, there is an evaluation unit 36 ​​for determining the epipolar line, wherein corresponding information, such as information about the angle, is provided by the system controller. In addition, there is a display unit 34 for displaying the X-ray image, the determined epipolar line and the extrapolated motion axis. The medical X-ray system 38 can also have a memory unit 37.

[0051] Such a medical X-ray system 38 for implementing the method can be formed, for example, by a mobile C-arm X-ray device. In order to accurately determine the angle (position / orientation of X-ray source and X-ray detector) or the entire epipolar geometry, the encoder information of the axis of motion of the recording system can be read and used, for example. External sensors can also be used for positioning. The method uses the known position of the C-arm in order to generate a corresponding visualization on the projection image.

[0052] The present invention can be summarized as follows: in order to reliably monitor interventional interventions with longitudinal implants with the lowest possible X-ray dose, a method for monitoring surgical interventions using X-ray imaging is provided, wherein the X-ray imaging is performed by a shooting system that can be adjusted to different angles, the shooting system comprising an X-ray light source and an X-ray detector, during the intervention, an implant having a tip moves forward along a movement axis in the anatomical structure of the object under examination, the method comprising the following steps: shooting a first projection image of the implant at a first angle, after the implant moves forward, shooting a third projection image of the implant at a third angle, determining an initial position of the tip of the implant on the first projection image, determining an advanced position of the tip of the implant on the third projection image, determining a first epipolar line for the advanced position of the tip in the first projection image with the aid of an epipolar geometry relationship determined by the first angle and the third angle, and simultaneously showing the first projection image and the third projection image, wherein the determined epipolar line is shown in the first projection image.

Claims

1. A method for monitoring a surgical intervention using X-ray imaging, the X-ray imaging being performed using a recording system adjustable to different angles, the recording system having an X-ray light source and an X-ray detector, in which an implant with a tip is moved forwards with the tip along a movement axis in an anatomical structure of an object under examination, the method comprising the following steps: capturing a first projection image of the implant at a first angle, After the implant moves forward, taking a third projection image of the implant at a third angle, (optionally) determining an initial position of the tip of the implant on the first projection image, determining the advanced position of the tip of the implant on the third projection image, determining a first epipolar line for the advanced position of the tip in the first projection image using the epipolar geometry determined by the first angle and the third angle, and The first projection image and the third projection image are shown simultaneously, wherein the determined epipolar line is shown in the first projection image.

2. The method according to claim 1, characterized in that The method comprises the additional steps of: taking a second projection image of the implant at a second angle different from the first angle before the forward movement, determining the initial position of the tip of the implant on the second projection image, determining a second epipolar line for the advanced position of the tip in the second projection image using the epipolar geometry determined by the second angle and the third angle, and The second projection image is shown simultaneously with the first projection image and the third projection image, and the determined second epipolar line is shown in the second projection image.

3. The method according to claim 1 or 2, wherein: Furthermore, the (projected) axis of movement of the forward movement of the tip of the implant is shown in the first projection image and / or in the second projection image.

4. The method according to claim 3, wherein: The axis of movement is determined as an extrapolation of the longitudinal axis of the instrument and is shown in the first projection image and / or the second projection image.

5. The method according to claim 4, wherein: The corresponding intersection points of the epipolar lines with the axis of motion are determined and shown.

6. A method according to any one of the preceding claims, wherein: Image recognition is performed to determine the initial position and / or the advanced position and / or the implant on the projection image.

7. A method according to any one of the preceding claims, wherein: The third angle is different from the first angle and the second angle.

8. The method according to any one of claims 1 to 6, wherein: The third angle is the same as the first angle or the second angle.

9. A method according to any one of the preceding claims, wherein: The first projection image, the second projection image and / or the third projection image are displayed side by side with each other and / or one above the other.

10. A method according to any one of the preceding claims, wherein: The movement axis is faded in and / or drawn in and / or marked in the projection image.

11. A method according to any one of the preceding claims, wherein: At least one additional projection image is captured at a third angle, and additional advanced positions of the tip of the implant are determined in each of the additional projection images. Additional epipolar lines are determined in the first projection image and the second projection image through the epipolar geometric relationship determined by the first angle and the third angle and / or the second angle and the third angle together with the advanced position of the tip, and the determined additional epipolar lines are shown in the first projection image and the second projection image.

12. A medical X-ray system (38) for implementing the method according to any one of the preceding claims 1 to 10, comprising: An X-ray imaging device, which is used to take X-ray images and comprises a photographing system (30) which can be adjusted to different angles, the photographing system having an X-ray light source (31) and an X-ray detector (32), a system control unit (33) for controlling a medical X-ray system, an imaging system (35) for analyzing X-ray images, in particular for image recognition, an evaluation unit (36) for determining the epipolar lines, and A display unit (43) is used to display the X-ray image and the epipolar line.

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